Shell Waste Management and Utilization: Mitigating Organic Pollution and Enhancing Sustainability

Every year, close to 8 million tons of waste crab, shrimp and lobster shells are produced globally, as well as 10 million tons of waste oyster, clam, scallop and mussel shells. The disposed shells are frequently dumped at sea or sent to landfill, where they modify soils, waters and marine ecosystems. Waste shells are a major by-product, which should become a new raw material to be used to the best of their potential. There are a number of applications for waste shells in many fields, such as agriculture, medicine, chemical production, construction, environmental protection, cosmetic industry, food and feed industry, and a plethora of other (often niche) applications, which are being developed by the day. This review provides a broad picture of crustacean and mollusc shell waste management and reutilization possibilities, reviewing well established, current, and potential strategies, particularly from the standpoint of sustainability challenges and energy demand

Seasonal antioxidant and biochemical properties of the Northern Adriatic Pecten jacobaeus

The present work is the first study of Mediterranean scallop (Pecten jacobaeus) biochemical properties, antioxidant defenses, and free radical scavengers during the yearly seasons in the Northern Adriatic, off Istria. Scallop nutrient reserves (glucose, triglyceride, and cholesterol) in four tissues under examination were positively correlated and were predominant in digestive gland and gonad. The muscle energy maxima were in correlation with the maximum fall gonosomatic index (GSI), when diatoms and coccolithophorids thrive. The decrease of GSI in summer might be related to the spawning or resorption of gametes. Summer also revealed elevated levels of glucose in gonad and digestive gland, while muscle glucose and cholesterol significantly varied in spring vs. winter samples. In relation to the diatom seasonal abundance, carotenoids, namely astaxanthin peaks were found in digestive gland, which, being stimulators of calcium transport over cell membranes, could have contributed to the high digestive gland levels of calcium in winter. In winter, total antioxidative status (TAS) of scallop tissues was 3-fold higher than in other seasons, particularly in digestive gland, having a significant correlation with magnesium, a regulatory tool in oxidative processes. The winter maxima of TAS and thiobarbituric acid reactive substances TBARS in relation to summer maxima of glutathione peroxidase and superoxide dismutase in digestive glands indicate to a decrease in antioxidant defense during cold months, and are related to the accumulation of lipid peroxidation products (such as malondialdehyde) in digestive gland of scallops. Although the increased susceptibility to oxidative stress could be attributed to winter temperature, other factors such as the gonad maturation, availability of food supply, and salinity might counteract that effect. The seawater alterations of salinity, temperature and water quality are in relation to the river Po influx, which is very likely to influence the physiological and biochemical responses of scallops in the Northern Adriatic

Comparative Tissue Responses of Marine Mollusks on Seasonal Changes in the Northern Adriatic Sea

In the shallow Northern Adriatic, marine mollusks are affected by bottom trawling and seafood disturbance. Seasonal oscillations of oceanographic factors additionally influence their physiology, stress responses and survival. Tissue responses to seasonal variations in green ormer (Haliotis tuberculata L.) and Mediterranean scallop (Pecten jacobaeus L.) in the Northern Adriatic have not been reported. Hence, their biochemical and antioxidant defense properties over seasons were studied and the microanatomical structure of their tissue was correlated with function. Histological analysis of gonads revealed two peaks of gonadal maturation and spawning during the spring/summer period and winter season for scallops, and one peak during the fall for ormers. The gonadal maturation of both species was correlated with their seasonal variations of metabolic demands and antioxidant capacity. The lipid vacuoles of tubuloacinar terminations in the digestive gland differed between the two species ; in scallop they are several-fold larger in size and number. Low temperatures in winter contributed to a decline in enzymatic antioxidant defense in scallop tissues, having lower superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity, and higher concentrations of thiobarbituric acid reactive substances (TBARS) and total antioxidant status (TAS). In ormers, winter induced lower TAS, TBARS, SOD and GPx concentrations. The significant difference of winter TAS and TBARS levels between ormers and scallops was correlated with variations in their reproductive cycles, as well as in antioxidant defense systems. The most important factor for stress-related parameters for both species in this work was found to be the season-induced temperature chang

Seasonal impact on biochemical, structural and fatty acid properties of Mediterranean scallop Pecten jacobaeus (Linnaeus, 1758) tissues from the Northern Adriatic

Jakovljeva kapica (Pecten jacobaeus, L.) endemski je školjkaš u Mediteranu. Prirodno se u većem broju pojavljuje samo u sjevernom Jadranu. Na području sjeverozapadne Istre jakovljeva kapica relativno je čest nalaz i lovi se u komercijalne svrhe. Poznavanje fiziološkog statusa jakovljeve kapice analizom biokemijskih, lipidnih i masnokiselinskih značajki pojedinih tkiva te histološkog statusa tijekom sezona važno je radi njezina očuvanja u prirodnom okolišu te mogućeg uzgoja. U tkivima gonada ustanovljena je sezonalna varijacija razvojnih stadija te produženi reproduktivni ciklus s dva razdoblja mrijesta. Dokazana je značajna uloga energetskih metabolita i lipida u otpornosti kapica na stres prouzročen temperaturnim ekstremima. Uočeno je smanjenje antioksidativne obrane tijekom hladnih mjeseci, uz nakupljanje produkata lipidne peroksidacije u tkivima. Sastav masnih kiselina jakovljeve kapice razlikuje se između tkiva i sezona te ukazuje na to da je mišić, koji je razlog komercijalne eksploatacije, najbolji za konzumaciju u proljeće i ljeto, jer je zbroj nezasićenih masnih kiselina (MUFA i PUFA) mišića veći od 50 % u ukupnim lipidima. Omjeri n-3/n-6 masnih kiselina su u tom periodu najveći, a vrijednosti kolesterola i glukoze najniže. Rezultati istraživanja upućuju na to da su uvjeti okoliša (temperatura mora) i reproduktivno razdoblje glavni procesi koji utječu na sezonalne obrasce biokemijskih i masnokiselinskih parametara jakovljeve kapice.Mediterranean scallop (Pecten jacobaeus, L.) is the endemic bivalve of the Mediterranean. It naturally occurs in larger quantities only in the Northern Adriatic. In the Northwestern Istria, Mediterranean scallop is a relatively common finding, fished for commercial purposes. Overfishing of the species may occur because of a small fishing area and high market value. Knowledge of the physiological status of the Mediterranean scallop through analyzing the biochemical, lipid and fatty acid structure of tissues as well as histological status during the seasons is important for its preservation in the natural environment and possible aquaculture. The aim of the research was to examine the seasonal impact in both sexes and four tissues (gills, digestive gland, gonads, muscle) on biochemical indicators (concentration of metabolites, proteins/enzymes, electrolytes, antioxidant capacity, status of lipids and fatty acids (saturated, monounsaturated, polyunsaturated, omega-3 and omega-6 fatty acids)) and histological-morphological characteristics. Shellfish were collected seasonally (spring, summer, autumn and winter) by a bottom trawl three nautical miles off the Western Istria coast. The seabed of covered area was predominantly sandy with maximum depth of 40 meters. Upon hauling, the catch was emptied on the deck, scallops were separated from the rest of the catch, sorted, counted and transported on ice to the coast. There they were inspected for external signs of mechanical damage, wet weighed and measured (total mass of the shellfish, mass of soft tissue, mass of individual organs, length and width of the shell). Based on the measured data, the length-weigth ratio, condition index (IK) and gonadosomatic index (GSI) were calculated. The samples determined for the measurement of biochemical indicators, lipid and fatty acid status were placed in polyethylene bags with sealing strips. After that, the samples were frozen and kept at -86 ˚C. Samples for histological-morphological analyzes were not frozen, but stored in a 4% formalin solution. Hydrographic parameters (sea temperature, salinity and dissolved oxygen) were measured during seasons. Four scallop tissues were studied for the selected biochemical properties, antioxidant defenses and free radical scavengers. These included tissue magnesium (Mg), calcium (Ca), glucose (GLU), triglyceride (TRIG), and cholesterol (CHOL) concentrations, activities of lactate dehydrogenase (LDH), superoxide dismutase (SOD), glutathione peroxidase (GPx), total antioxidant status (TAS), malondialdehyde (MDA), total carotenoid and astaxanthin contents. Total lipids and fatty acids were analyzed in the digestive gland, muscle and gonads. Fatty acids were grouped according to their degree of saturation, as saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids, and as omega-3 (n-3), omega-6 (n-6), and omega-9 (n-9) fatty acids. The research results indicate that environmental conditions (sea temperature) and the reproductive period are the main processes that influence the seasonal patterns of biochemical and fatty acid parameters of the Mediterranean scallop. Seasonal variation of developmental stages and an extended reproductive cycle showed strong gametogenic and reproductive activity in autumn (gamete maturation) and winter (spawning), with intensification of the gametogenic stage in warm months, when reproductive activity is at maximum, as well as summer spawning. The significant role of energy metabolites and lipids in the resistance of Mediterranean scallops to stress caused by temperature extremes was proven. A decrease in antioxidant defense was observed during the cold months, along with the accumulation of lipid peroxidation products in tissues. The carotenoid astaxanthin was the most abundant in the winter months. Given that carotenoids were most numerous in the tissue of the digestive gland, it is most likely that they were ingested through diet. As the energy reserves stored in the muscle are used for gamete development and vary with respect to the availability of food, it is possible to conclude that the catabolism of the muscle reserves did not take place due to the availability of food which was sufficient for both somatogenic and gametogenic growth of scallops. The fatty acid composition of Mediterranean scallop differed between tissues and seasons and indicates that muscle, which is the reason for commercial exploitation of the species, is best for consumption in spring and summer, because the sum of unsaturated fatty acids (MUFA and PUFA) was greater than 50% in total lipids. The n-3/n-6 fatty acid ratios were the highest in that period, while cholesterol and glucose values were the lowest

Seasonal impact on biochemical, structural and fatty acid properties of Mediterranean scallop Pecten jacobaeus (Linnaeus, 1758) tissues from the Northern Adriatic

Jakovljeva kapica (Pecten jacobaeus, L.) endemski je školjkaš u Mediteranu. Prirodno se u većem broju pojavljuje samo u sjevernom Jadranu. Na području sjeverozapadne Istre jakovljeva kapica relativno je čest nalaz i lovi se u komercijalne svrhe. Poznavanje fiziološkog statusa jakovljeve kapice analizom biokemijskih, lipidnih i masnokiselinskih značajki pojedinih tkiva te histološkog statusa tijekom sezona važno je radi njezina očuvanja u prirodnom okolišu te mogućeg uzgoja. U tkivima gonada ustanovljena je sezonalna varijacija razvojnih stadija te produženi reproduktivni ciklus s dva razdoblja mrijesta. Dokazana je značajna uloga energetskih metabolita i lipida u otpornosti kapica na stres prouzročen temperaturnim ekstremima. Uočeno je smanjenje antioksidativne obrane tijekom hladnih mjeseci, uz nakupljanje produkata lipidne peroksidacije u tkivima. Sastav masnih kiselina jakovljeve kapice razlikuje se između tkiva i sezona te ukazuje na to da je mišić, koji je razlog komercijalne eksploatacije, najbolji za konzumaciju u proljeće i ljeto, jer je zbroj nezasićenih masnih kiselina (MUFA i PUFA) mišića veći od 50 % u ukupnim lipidima. Omjeri n-3/n-6 masnih kiselina su u tom periodu najveći, a vrijednosti kolesterola i glukoze najniže. Rezultati istraživanja upućuju na to da su uvjeti okoliša (temperatura mora) i reproduktivno razdoblje glavni procesi koji utječu na sezonalne obrasce biokemijskih i masnokiselinskih parametara jakovljeve kapice.Mediterranean scallop (Pecten jacobaeus, L.) is the endemic bivalve of the Mediterranean. It naturally occurs in larger quantities only in the Northern Adriatic. In the Northwestern Istria, Mediterranean scallop is a relatively common finding, fished for commercial purposes. Overfishing of the species may occur because of a small fishing area and high market value. Knowledge of the physiological status of the Mediterranean scallop through analyzing the biochemical, lipid and fatty acid structure of tissues as well as histological status during the seasons is important for its preservation in the natural environment and possible aquaculture. The aim of the research was to examine the seasonal impact in both sexes and four tissues (gills, digestive gland, gonads, muscle) on biochemical indicators (concentration of metabolites, proteins/enzymes, electrolytes, antioxidant capacity, status of lipids and fatty acids (saturated, monounsaturated, polyunsaturated, omega-3 and omega-6 fatty acids)) and histological-morphological characteristics. Shellfish were collected seasonally (spring, summer, autumn and winter) by a bottom trawl three nautical miles off the Western Istria coast. The seabed of covered area was predominantly sandy with maximum depth of 40 meters. Upon hauling, the catch was emptied on the deck, scallops were separated from the rest of the catch, sorted, counted and transported on ice to the coast. There they were inspected for external signs of mechanical damage, wet weighed and measured (total mass of the shellfish, mass of soft tissue, mass of individual organs, length and width of the shell). Based on the measured data, the length-weigth ratio, condition index (IK) and gonadosomatic index (GSI) were calculated. The samples determined for the measurement of biochemical indicators, lipid and fatty acid status were placed in polyethylene bags with sealing strips. After that, the samples were frozen and kept at -86 ˚C. Samples for histological-morphological analyzes were not frozen, but stored in a 4% formalin solution. Hydrographic parameters (sea temperature, salinity and dissolved oxygen) were measured during seasons. Four scallop tissues were studied for the selected biochemical properties, antioxidant defenses and free radical scavengers. These included tissue magnesium (Mg), calcium (Ca), glucose (GLU), triglyceride (TRIG), and cholesterol (CHOL) concentrations, activities of lactate dehydrogenase (LDH), superoxide dismutase (SOD), glutathione peroxidase (GPx), total antioxidant status (TAS), malondialdehyde (MDA), total carotenoid and astaxanthin contents. Total lipids and fatty acids were analyzed in the digestive gland, muscle and gonads. Fatty acids were grouped according to their degree of saturation, as saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids, and as omega-3 (n-3), omega-6 (n-6), and omega-9 (n-9) fatty acids. The research results indicate that environmental conditions (sea temperature) and the reproductive period are the main processes that influence the seasonal patterns of biochemical and fatty acid parameters of the Mediterranean scallop. Seasonal variation of developmental stages and an extended reproductive cycle showed strong gametogenic and reproductive activity in autumn (gamete maturation) and winter (spawning), with intensification of the gametogenic stage in warm months, when reproductive activity is at maximum, as well as summer spawning. The significant role of energy metabolites and lipids in the resistance of Mediterranean scallops to stress caused by temperature extremes was proven. A decrease in antioxidant defense was observed during the cold months, along with the accumulation of lipid peroxidation products in tissues. The carotenoid astaxanthin was the most abundant in the winter months. Given that carotenoids were most numerous in the tissue of the digestive gland, it is most likely that they were ingested through diet. As the energy reserves stored in the muscle are used for gamete development and vary with respect to the availability of food, it is possible to conclude that the catabolism of the muscle reserves did not take place due to the availability of food which was sufficient for both somatogenic and gametogenic growth of scallops. The fatty acid composition of Mediterranean scallop differed between tissues and seasons and indicates that muscle, which is the reason for commercial exploitation of the species, is best for consumption in spring and summer, because the sum of unsaturated fatty acids (MUFA and PUFA) was greater than 50% in total lipids. The n-3/n-6 fatty acid ratios were the highest in that period, while cholesterol and glucose values were the lowest